In the production of semiconductor devices and liquid crystal displays, rapid progress has recently been made in fining of the size of them with the progress of a lithography technology. As a technique for fining of the size, shortening of the wavelength of an exposure light source is generally performed. Specifically, while ultraviolet rays typified by g-ray and i-ray have conventionally been used, KrF excimer laser (248 nm) is popularly used for mass production at present and ArF excimer laser (193 nm) begins to be introduced for mass production. Also a lithography technology using F2 excimer laser (157 nm), EUV (extreme ultraviolet ray) and EB (electron beam) as a light source (radiation source) has been studied.
To a resist for a light source having a short wavelength, high resolution capable of reproducing a pattern having a fine size and high sensitivity to the light source having a short wavelength are required. As one resist which satisfies these conditions, a chemically amplified photoresist comprising a base resin and an acid generator which generates an acid upon exposure (hereinafter referred to as PAG) is known and the chemically amplified photoresist includes a positive photoresist in which alkali solubility of the exposed area increases and a negative photoresist in which alkali solubility of the exposed area decreases.
As a base resin of the chemically amplified photoresist, there has hitherto been used a resin (PHS-based resin) in which a hydroxyl group of polyhydroxystyrene (PHS) having high transparency to KrF excimer laser (248 nm) is protected with an acid dissociable dissolution inhibiting group. However, the PHS-based resin has an aromatic ring such as benzene ring and is therefore insufficient in transparency to light having a wavelength shorter than 248 nm, for example, 193 nm. Therefore, the chemically amplified photoresist containing the PHS-based resin as a base resin component had such a drawback that it shows low resolution in the process using light having a wavelength of 193 nm.
Therefore, as the base resin of the resist in ArF excimer laser lithography, a resin (acrylic resin) comprising a constituent unit derived from a (meth)acrylate ester in a main chain is mainly used because it is excellent in transparency to light having a wavelength of about 193 nm. As disclosed in Japanese Patent 2,881,969, as the acid dissociable dissolution inhibiting group, a constituent unit derived from a tertiary ester compound of (meth)acrylic acid, for example, 2-alkyl-2-adamanthyl (meth)acrylate is generally used. The constituent unit is known that the acid dissociable dissolution inhibiting group has high elimination energy.